what is panspermia and how louis pasteur use this term and hence explain spontaneous theory?

Panspermia is a hypothesis which states that life is present across the universe and is distributed by meteoroids, asteroids etc.

For a long time it was also believed that life came out of decaying and rotting matter like straw, mud, etc. This was the theory of spontaneous generation. Louis Pasteur by careful experimentation demonstrated that life comes only from pre-existing life. He showed that in pre-sterilised flasks, life did not come from killed yeast while in another flask open to air, new living organisms arose from ‘killed yeast’. Spontaneous generation theory was dismissed once and for all.

Louis pasteur disproved the theory of spontaneous generation.